21.One advantage of fishing is ______ it can give you a lot of pleasure.
A. how B. why C. that D. when
22. Jack, together with his sisters,_____ great interest in writing these days.
A. show B. will show C. are showing D. is showing
23. According to the survey, modern industry_____ quickly in developing countries in the past half century.
A. develop B. has developed C. had developed D. developed
